Low-fat dressings have less health benefits than full fat

It might be tempting to reach for a low-fat salad dressing if you're trying to lose weight, but you could be sacrificing other health benefits, according to a new study.

Researchers from Iowa State University in the US found that people absorb more carotenoids — compounds in vegetables that help prevent illnesses such as heart disease and cancer — if they eat dressings with higher fat content.

They fed 29 people salads dressed with saturated fat, monounsaturated fat and polyunsaturated fat, then tested their blood to see how much carotenoids they had absorbed from the vegetables in the salad.

They found dressings rich in monounsaturated fat — such as canola and olive oil — required the least amount of fat to get the most carotenoid absorption. But when they used butter — high in saturated fat — and corn oil — high in polyunsaturated fat — the subjects required a lot more fat to get the same carotenoid absorption.

"If you want to utilise more from your fruits and vegetables, you have to pair them correctly with fat-based dressings," said Mario Ferruzzi, the study's lead author and a Purdue associate professor of food science.

"If you have a salad with a fat-free dressing, there is a reduction in calories, but you lose some of the benefits of the vegetables."

Three grams of the monounsaturated fat dressings allowed the subjects to absorb just as much carotenoids as 20 grams, making it a good option for people who want to reduce their fat intake but get maximum absorption of carotenoids from the vegies in their salad.

"Even at the lower fat level, you can absorb a significant amount of carotenoids with monounsaturated fat-rich canola oil," Ferruzzi said. "Overall, pairing with fat matters. You can absorb significant amounts of carotenoids with saturated or polyunsaturated fats at low levels, but you would see more carotenoid absorption as you increase the amounts of those fats on a salad."

However, don't take this as a green light to go crazy with the ceaser dressing. Dietitian Susie Burrell (sussieburrell.com.au) warns that extra fat in the diet can lead to high cholesterol, a factor in heart disease.

"One of the biggest issues with actively adding fat into the diet," she said, "is that we tend to go overboard — a teaspoon of high fat dressing becomes two tablespoons and an extra 20-40g of fat. As we only need 40-60g of fat a day, it can be easy to overdo things and be consuming extra saturated fat that is readily stored and can contribute to high blood cholesterol levels in the body."